Substrate processing method, manufacturing method of euv mask, and euv mask

ABSTRACT

According to the substrate processing method in the embodiments, as a mask substrate used for forming an EUV mask, a mask substrate in which a first film having a first hydrophilicity is formed on one main surface and a resist is applied to another main surface is exposed from a side of the resist. Then, a hydrophilic treatment is performed on a surface of the first film to make the surface of the first film have a second hydrophilicity larger than the first hydrophilicity. Then, a development treatment of the resist is performed with respect to the mask substrate in which the hydrophilic treatment is performed on the surface of the first film to have the second hydrophilicity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 13/034,143, filed Feb. 24,2011, which is incorporated herein by reference.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2010-40500, filed on Feb. 25,2010; the entire contents of which are incorporated herein by reference.

FIELD

The present embodiments typically relate to a substrate processingmethod, a manufacturing method of an EUV mask, and an EUV mask.

BACKGROUND

Conventionally, a transmissive mask whose back surface is composed ofglass (Qz) has been used as a photomask. Organic matter is difficult toadhere to Qz due to its surface condition, so that adhesion of particlesto the back surface does not substantially arise as a problem. On theother hand, an EUV mask (EUV exposure mask) is a reflective mask, sothat an exposure process needs to be performed in a state where the EUVmask is electrostatically chucked. Therefore, a conductive film isformed on the back surface of the EUV mask. For the conductive film, amaterial, to which organic particles are easy to adhere, is often used,and adhered organic particles are difficult to clean in a cleaningprocess thereafter. If organic particles are adhered to the conductivefilm, the EUV mask distorts when the back surface of the EUV mask iselectrostatically chucked, so that a dimension or a position of anexposed wafer pattern is misaligned from a desired value.

Moreover, when manufacturing the EUV mask, if a film is attached to theback surface of the EUV mask, poor drying (droplet residue) occurs aftera development treatment. Then, impurities including carbon in the airadhere to liquid remaining on the back surface, which results incontaminating the back surface of the EUV mask. Therefore, acountermeasure is needed against contamination (particles or dropletresidue defects) of not only the front surface but also the back surfacein the EUV mask.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 1F are diagrams illustrating a manufacturing procedureof an EUV mask according to a first embodiment;

FIG. 2 is a diagram illustrating a configuration of a manufacturingsystem of the EUV mask;

FIG. 3 is a diagram illustrating a relationship between an irradiationenergy of UV light to a conductive film and a contact angle of theconductive film;

FIG. 4 is a diagram illustrating a relationship between the contactangle of the conductive film and a droplet residue on the conductivefilm;

FIG. 5A to FIG. 5C are diagrams for explaining specific examples of anUV irradiating method; and

FIG. 6A and FIG. 6B are diagrams illustrating a hydrophilic treatmentprocedure by an oxidizing liquid to a substrate.

DETAILED DESCRIPTION

According to a substrate processing method in embodiments, as a masksubstrate used for forming an EUV mask, a mask substrate in which afirst film having a first hydrophilicity is formed on one main surfaceand a resist is applied to another main surface is exposed from a sideof the resist. Then, a hydrophilic treatment is performed on a surfaceof the first film to make the surface of the first film have a secondhydrophilicity larger than the first hydrophilicity. Then, a developmenttreatment of the resist is performed with respect to the mask substratein which the hydrophilic treatment is performed on the surface of thefirst film to have the second hydrophilicity.

A substrate processing method, a manufacturing method of an EUV mask,and an EUV mask according to the embodiments will be explained below indetail with reference to the accompanying drawings. The presentinvention is not limited to these embodiments.

First Embodiment

A substrate processing method according to the present embodiment is,for example, used in a pattern formation in a semiconductormanufacturing process (wafer process, exposure mask manufacturingprocess, and the like) or a liquid-crystal-device manufacturing process.In the following, the case is explained in which the substrateprocessing method is applied to a manufacturing process of an EUV maskused in EUV (Extreme Ultra-Violet) lithography.

FIG. 1A to FIG. 1F are diagrams illustrating the manufacturing procedureof the EUV mask according to the first embodiment, and FIG. 2 is adiagram illustrating a configuration of a manufacturing system of theEUV mask. When manufacturing an EUV (Extreme Ultra-Violet) mask 200, anEUV mask blank (EUV exposure mask blank) is manufactured in advance. Inthe following, the EUV mask blank on which a resist R1 to be describedlater is formed is called a substrate (mask substrate) 100.

The manufacturing system of the EUV mask includes an electron-beamlithography apparatus 51, a PEB apparatus 52, an UV-light irradiatingapparatus (UV irradiating unit) 53, a developing apparatus (developingtreatment unit) 54, and a drying apparatus 55. The electron-beamlithography apparatus 51 is an apparatus that irradiates the substrate100 with exposure light by EB (electron beam). The PEB apparatus 52 isan apparatus that heats (PEB: Post Exposure Baking) the exposedsubstrate 100, and the developing apparatus 54 is an apparatus thatperforms development on the substrate 100. The UV-light irradiatingapparatus 53 is an apparatus that performs hydrophilization on thesubstrate 100 and includes a UV light source 31 that irradiates the backsurface of the substrate 100 with UV light. The drying apparatus 55 isan apparatus that dries the substrate 100 after development. Thesubstrate 100 to which the resist R1 is applied is conveyed to eachapparatus in the order of the electron-beam lithography apparatus 51,the PEB apparatus 52, the UV-light irradiating apparatus 53, thedeveloping apparatus 54, and the drying apparatus 55 to be processed ineach apparatus.

The EUV mask blank (the substrate 100 before the resist R1 is applied)is configured to include a glass substrate Qz having a low thermalexpansion property, and a conductive film (back surface film) M isformed on the back surface side (lower surface) of the glass substrateQz. Moreover, a light-shielding film (not shown) and a reflective film 1are formed on the front surface side (upper surface) of the glasssubstrate Qz.

The surface on the front side of the EUV mask blank is a surface on aside that is irradiated with EUV light when performing an EUV exposureby using the EUV mask. The reflective film 1 is a film that isirradiated with the EUV light and reflects the EUV light onto the waferside when performing the EUV exposure.

Moreover, the surface on the back side of the EUV mask blank is asurface on a side that is electrostatically chucked when performing theEUV exposure by using the EUV mask. The conductive film M iselectrostatically chucked by an EUV exposure apparatus 61 to bedescribed later when performing the EUV exposure. The conductive film Mis a film that includes metal such as chrome (Cr) and is a film whosehydrophilicity is not high.

As shown in FIG. 1A, for manufacturing the EUV mask 200, for example,the positive-type chemically-amplified resist R1 is formed on the uppersurface side of the reflective film 1 in advance. Consequently, in thesubstrate 100 used for manufacturing the EUV mask 200, a processingtarget film including a photosensitive thin film is formed on the frontsurface and a thin film having conductivity is formed on the backsurface in advance.

After forming the resist R1 on the upper surface side of the reflectivefilm 1, as shown in FIG. 1B, exposure light such as EB is emitted fromabove the resist R1 by the electron-beam lithography apparatus 51 to aposition corresponding to a formation position of a mask pattern.Consequently, exposure to the resist R1 is performed and a latent imageis formed at the position corresponding to the formation position of themask pattern in the resist R1.

Then, as shown in FIG. 1C, heating (PEB) of the substrate 100 isperformed by the PEB apparatus 52. Consequently, a sensitizer of theresist R1 is diffused. A portion (position at which the mask pattern isformed) that is not irradiated with exposure light in the resist R1 isdissolved sparingly in a developer. On the other hand, a portion(position at which the mask pattern is not formed) that is irradiatedwith exposure light is dissolved in a developer. In FIG. 1C, a resistregion insolubilized to a developer is illustrated as the resist R1 anda resist region that is not insolubilized to a developer is illustratedas a resist R2.

Thereafter, as shown in FIG. 1D, the conductive film M that is the backsurface side of the substrate 100 is irradiated with UV light from theUV light source 31 of the UV-light irradiating apparatus 53 as one ofthe substrate processes. In other words, the back surface side of thesubstrate 100 is irradiated with UV light before the developmenttreatment is started after the PEB treatment. Consequently, ozone (O₃)is generated. Then, the generated ozone oxidizes the surface of theconductive film M and, as a result, the hydrophilicity of the surface ofthe conductive film M increases. When irradiating the conductive film Mwith UV light, a configuration and a process condition are selected sothat a pattern dimension or a defect on the surface of the substrate 100is not affected.

After the hydrophilicity of the conductive film M is increased by the UVlight irradiation, the substrate 100 is immediately conveyed to thedeveloping apparatus 54. Then, as shown in FIG. 1E, the developmenttreatment of the substrate 100 is performed in the developing apparatus54. Specifically, a developer 21 is supplied (dropped or sprayed) fromthe front surface side of the substrate 100 to the whole front surfaceof the substrate 100. Consequently, the resist R2 is removed from thesubstrate 100 and the resist R1 remains on the substrate 100, whereby aresist pattern is formed on the substrate 100. Moreover, as a backsurface rinsing treatment, a rinse liquid 22 such as pure water isapplied from the back surface side of the substrate 100 to the wholeback surface of the substrate 100. Consequently, the back surface of thesubstrate 100 is rinsed.

In the present embodiment, because the hydrophilic treatment isperformed on the conductive film M, even if the developer 21 flowsaround to the conductive film M side in the development treatment to thesubstrate 100, the developer 21 hardly remains on the conductive film Mby performing the rinsing treatment. Moreover, after the rinse liquid 22is applied to the substrate 100, the rinse liquid 22 hardly remains onthe conductive film M.

It is desirable to pre-wet the substrate 100 with liquid such as purewater that does not react with the substrate 100 before developing theresist R1 applied to the front surface of the substrate 100 for making atreatment temperature of the substrate 100 constant. When thetemperature change of the substrate 100 by the UV irradiation is small,pre-wetting of the substrate 100 can be omitted.

Moreover, if a long period of time elapses after the UV irradiation,carbon contaminant in an ambient atmosphere of the substrate 100 occurson the back surface of the substrate 100 and whereby the hydrophiliceffect decreases over time. Therefore, it is desirable to start thedevelopment treatment of the substrate 100 within five minutes.

Thereafter, as shown in FIG. 1F, drying of the substrate 100 isperformed by the drying apparatus 55. The drying apparatus 55 performsdrying of the substrate 100 while rotating the substrate 100 in a planeparallel to the main surface. Then, the reflective film 1 is etched fromabove the resist R1, and thereafter the resist R1 is removed, wherebythe EUV mask 200 is completed. After the EUV mask 200 is completed, theEUV mask 200 is conveyed to the EUV exposure apparatus 61 and the EUVexposure treatment is performed on a wafer.

In this manner, in the present embodiment, before developing thesubstrate 100 in which the conductive film M (first film) having a firsthydrophilicity is formed on one main surface and the resist R1 isapplied to the other main surface, the hydrophilic treatment isperformed on the surface of the conductive film M by oxidizing thesurface of the conductive film M. Consequently, the surface of theconductive film M is hydrophilized to have a second hydrophilicitylarger than the first hydrophilicity. Then, after performing thehydrophilic treatment on the conductive film M, the developmenttreatment is performed on the substrate 100.

In other words, in the present embodiment, before (for example,immediately before) performing the development treatment (back surfacerinsing and drying) that is the first liquid treatment to the substrate100, hydrophilization of the conductive film M is performed. Therefore,it is possible to prevent adhesion of particles to the conductive film Min the development treatment to the substrate 100, generation of adroplet residue defect when drying the substrate 100, and the like.Thus, contamination of the conductive film M can be prevented.

The hydrophilic treatment of the conductive film M can be performedbefore any process so long as it is the first liquid treatment to thesubstrate 100. When it takes a predetermined period of time or more fromthe hydrophilic treatment of the conductive film M to the developmentprocess to the substrate 100, the ambient atmosphere of the substrate100 is controlled until the development process so that thehydrophilicity of the conductive film M is not deteriorated.

Explanation is given for a relationship between an irradiation energy ofUV light to the conductive film M and a contact angle of the conductivefilm M and a relationship between the contact angle of the conductivefilm M and the droplet residue on the conductive film M. FIG. 3 is adiagram illustrating the relationship between the irradiation energy ofUV light to the conductive film and the contact angle of the conductivefilm. FIG. 4 is a diagram illustrating the relationship between thecontact angle of the conductive film and the droplet residue on theconductive film. In FIG. 3, a horizontal axis indicates the irradiationenergy of UV light to the conductive film M and a vertical axisindicates the contact angle of the conductive film M. Moreover, in FIG.4, a horizontal axis indicates the contact angle of the conductive filmM and a vertical axis indicates the remaining number of droplets (thenumber of droplets) on the conductive film M. The relationship shown inFIG. 4 is y=26.587x−1.7197 and R²=0.9988.

The contact angle of the conductive film M is an angle that a droplet(for example, the rinse liquid 22) on the conductive film M forms withrespect to the film surface of the conductive film M, and the contactangle becomes smaller as the hydrophilicity becomes higher. As shown inFIG. 3, it is found that when the conductive film M is irradiated withUV light with the irradiation energy of about 100 mJ, the contact angletakes approximately a constant value of 5° or less. Moreover, as shownin FIG. 4, when the contact angle is 5° or less, the number of dropletsbecomes small (50 or less). Therefore, the number of droplet residuedefects can be reduced by performing the UV irradiation to theconductive film M for a treatment time with which the contact anglebecomes about 5° or less with margin.

For example, an allowable value of the number of droplets is preset.Then, the contact angle with which this allowable value can be satisfiedis derived based on the relationship shown in FIG. 4. Moreover, theirradiation energy with which the contact angle calculated based on therelationship shown in FIG. 4 can be ensured is derived based on therelationship shown in FIG. 3. Consequently, the number of dropletresidue defects can be reduced to a desired value (allowable value) orless.

Next, specific examples of the UV irradiating method are explained. FIG.5A to FIG. 5C are diagrams for explaining the specific examples of theUV irradiating method. When performing the UV irradiation from the backsurface side of the substrate 100, it is desirable that the UVirradiation is performed so that UV light does not reach the resists R1and R2 on the front surface of the substrate 100. Therefore, forexample, as shown in FIG. 5A, a light guide 32 for preventing diffusionof UV light is arranged between the UV light source 31 and theconductive film M in the UV-light irradiating apparatus 53. The lightguide 32 has a tubular shape (that includes cylindrical shape andprismatic shape) to cover the gap between the UV light source 31 and theconductive film M. Moreover, the light guide 32 is, for example, formedof a material whose absorption in a UV light wavelength region is small,a material (low thermal expansion vitreous silica) that has a lowthermal expansion property even if it has a slight absorption, or thelike. Consequently, UV light emitted from the UV light source 31 isprevented from reaching the resists R1 and R2. Moreover, the irradiationamount of UV light emitted to the back surface of the conductive film Mbecomes uniform in the plane of the conductive film M.

Moreover, as shown in FIG. 5B, it is applicable to arrange a UVshielding plate 33 for preventing diffusion of UV light between the UVlight source 31 and the conductive film M in the UV-light irradiatingapparatus 53. The UV shielding plate 33 has a tubular shape to cover thegap between the UV light source 31 and the conductive film M. Moreover,the UV shielding plate 33 is formed of a member that can prevent leakageof UV light. Consequently, UV light emitted from the UV light source 31or ozone generated by UV light can be prevented from reaching theresists R1 and R2.

Furthermore, as shown in FIG. 5C, it is applicable to arrange a covermember 34 (for example, plate-shaped structure) that covers the surfacesof the resists R1 and R2 on the upper surface side of the substrate 100in the UV-light irradiating apparatus 53. The cover member 34 isarranged to be parallel to the main surface of the substrate 100 and inclose proximity to the front surface of the substrate 100. Consequently,UV light emitted from the UV light source 31 can be prevented fromreaching the resists R1 and R2.

Moreover, the UV light source 31 can be divided and arranged. Forexample, a plurality of the UV light sources 31 is arranged in theUV-light irradiating apparatus 53 and the conductive film M isirradiated with UV light by using the UV light sources 31. Consequently,the irradiation amount of UV light emitted to the back surface of theconductive film M becomes uniform in the plane of the conductive film M.

Furthermore, the UV irradiation to the substrate 100 can be performed bycombining the above UV irradiating methods. It is applicable to directlyirradiate the conductive film M with UV light from the UV light source31 without using the above UV irradiating methods.

After the EUV mask 200 is completed, a semiconductor device(semiconductor integrated circuit) is manufactured by using the EUV mask200 in the wafer process. Specifically, the EUV exposure apparatus 61performs the exposure treatment on the wafer by using the EUV mask 200,and thereafter the development treatment and the etching treatment tothe wafer are performed. In other words, a mask material is processedwith a resist pattern formed by transfer in the lithography process, andfurther, a processing target film is patterned by etching by using thepatterned mask material. The EUV mask 200 is manufactured for each layerwhen manufacturing a semiconductor device. Then, when manufacturing asemiconductor device, the exposure treatment, the development treatment,and the etching treatment are performed on the wafer for each layer byusing the EUV mask 200 manufactured for each layer.

In the present embodiment, the case is explained in which themanufacturing system of the EUV mask includes the PEB apparatus 52, theUV-light irradiating apparatus 53, the developing apparatus 54, and thedrying apparatus 55; however, theses apparatuses can be separateapparatuses or the configuration can be such that the apparatuses areincluded in one apparatus.

As above, according to the first embodiment, the conductive film M ishydrophilized before the development treatment process, so thatcontamination of the back surface of the EUV mask 200 when manufacturingthe EUV mask 200 can be prevented. Moreover, the contact angle of theconductive film M is set to 5° or less, the number of droplet residuedefects can be reduced. Consequently, TAT for a back surface inspectionof the EUV mask 200 performed after the development process can beshortened. Moreover, because the number of droplet residue defects isreduced, it becomes easy to perform a review of particles that wouldotherwise have to be removed, or the like. Therefore, it also becomeseasy to remove (clean or correct) particles adhered to the conductivefilm M. Thus, the production cost of the EUV mask 200 can be reduced andthe throughput can be improved.

Moreover, because the hydrophilic treatment to the conductive film M isperformed immediately before the development process, development of thesubstrate 100 can be performed before the hydrophilicity of theconductive film M is deteriorated. Thus, contamination of the backsurface of the EUV mask can be efficiently prevented.

Furthermore, the light guide 32, the UV shielding plate 33, the covermember 34, or the like is arranged in the UV-light irradiating apparatus53, so that the particle adhesion and the droplet residue on the frontsurface side of the substrate 100 can be efficiently prevented.

Second Embodiment

Next, the second embodiment of this invention is explained withreference to FIG. 6A and FIG. 6B. In the second embodiment, beforeperforming the development treatment on the substrate 100, theconductive film M is hydrophilized in advance by using liquid (oxidizingliquid 23 to be described later) having an oxidation effect instead ofthe UV irradiation.

In the similar manner to the first embodiment, the light shielding filmand the reflective film 1 are formed on the front surface of the maskblank. Moreover, the conductive film M is formed on the back surface ofthe mask blank. When manufacturing the EUV mask 200, the substrate 100in which the resist R1 is applied to the upper surface side of thereflective film 1 is exposed by the electron-beam lithography apparatus51, and thereafter the PEB is performed on the substrate 100 to form alatent image in the resist R1.

In the present embodiment, the hydrophilic treatment (back surfacetreatment) is performed only on the back surface side (the conductivefilm M) of the substrate 100 with the oxidizing liquid 23 havingoxidizability before starting the drying process in the developmenttreatment on the substrate 100 after the PEB treatment.

FIG. 6A and FIG. 6B are diagrams illustrating a manufacturing procedureof the EUV mask according to the second embodiment and illustrate ahydrophilic treatment procedure by an oxidizing liquid to the substrate.FIG. 6A and FIG. 6B illustrate the order of the back surface treatmentand the development to the substrate 100 as the hydrophilic treatmentprocedure to the substrate 100.

For example, as shown in FIG. 6A, the development (supply of thedeveloper 21) of the substrate 100 and the back surface treatment(supply of the oxidizing liquid 23) to the substrate 100 are performedsimultaneously. At this time, for enabling to fill the back surface ofthe substrate 100 with the oxidizing liquid 23 by the back surfacetreatment before the developer 21 flows around to the back surface ofthe substrate 100, it is applicable to adjust a development start timingor a start timing of the back surface treatment, an application amountof the developer 21 or the oxidizing liquid 23, or the like.

Moreover, as shown in FIG. 6B, development to the substrate 100 can beperformed after performing the back surface treatment on the substrate100. In this case, after filling the back surface of the substrate 100with the oxidizing liquid 23 as the back surface treatment to thesubstrate 100, the development treatment of the substrate 100 and theback surface rinsing of the substrate 100 are performed. The backsurface rinsing of the substrate 100 can be performed by the oxidizingliquid 23 or can be performed by the rinse liquid 22 such as pure water.

In the development treatment of the substrate 100, the developer flowsaround to the back surface and the back surface rinsing is performed, sothat the hydrophilic effect by the UV irradiation in the developmenttreatment becomes small. Moreover, difficulty in unit manufacturing isextremely high and is not realistic. On the other hand, in the presentembodiment, the oxidizing liquid 23 is supplied only to the back surfaceof the substrate 100, so that the hydrophilic treatment and developmenttreatment starts can be performed simultaneously.

As the oxidizing liquid 23 (chemical), for example, ozone water,sulfuric acid, hydrogen peroxide solution, or nitric acid is used. Theback surface treatment to the substrate 100 by the oxidizing liquid canbe performed before any process so long as it is performed before thefirst liquid treatment to the substrate 100.

As above, according to the second embodiment, because the conductivefilm M is hydrophilized with the oxidizing liquid 23 before thedevelopment treatment process, contamination of the back surface of theEUV mask when manufacturing the EUV mask 200 can be prevented.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1.-20. (canceled)
 21. A substrate processing system comprising: adeveloping apparatus; and a UV-light irradiating apparatus configuredto: carry a mask substrate therein, the mask substrate in which a firstfilm having a first hydrophilicity is formed on one main surface and aresist is applied to another main surface as the mask substrate, from aside of the resist; perform a hydrophilic treatment on a surface of thefirst film by irradiating the surface of the first film with a UV-lightto make the surface of the first film have a second hydrophilicitylarger than the first hydrophilicity; and perform a developmenttreatment of the resist with respect to the mask substrate in which thehydrophilic treatment is performed on the surface of the first film tohave the second hydrophilicity.
 22. The substrate processing systemaccording to claim 21, further comprising a drying apparatus to dry themask substrate after the development treatment.
 23. The substrateprocessing system according to claim 21, wherein: the UV-lightirradiating apparatus includes a light guide arranged between a UV-lightsource to irradiate the UV-light and the first film for preventingdiffusion of the UV-light, wherein the light guide is cylindrical inshape so as to cover in a gap between the UV-light source and the firstfilm.
 24. The substrate processing system according to claim 21,wherein: the UV-light irradiating apparatus includes a UV shieldingplate arranged between a UV-light source to irradiate the UV-light andthe first film for preventing diffusion of the UV-light, wherein the UVshielding plate is cylindrical in shape so as to cover in a gap betweenthe UV-light source and the first film.
 25. The substrate processingsystem according to claim 21, wherein: the UV-light irradiatingapparatus includes a cover member that covers a surface of the resist onthe mask substrate, and the cover member is arranged to be parallel tothe main surface of the mask substrate and in close proximity to a frontsurface of the mask substrate.
 26. The substrate processing systemaccording to claim 21, wherein: the UV-light irradiating apparatus isconfigured to perform the hydrophilic treatment such that a contactangle of the surface of the first film with respect to a rinse liquid 5°or less.
 27. The substrate processing system according to claim 21,wherein, after irradiating the surface of the first film with theUV-light and before developing the resist, the UV-light irradiatingapparatus is configured to pre-wet the mask substrate with a liquid thatdoes not react with the mask substrate.
 28. The substrate processingsystem according to claim 21, wherein, after irradiating the surface ofthe first film with the UV-light, the developing apparatus is configuredto perform the development treatment of the resist within five minutes.29. The substrate processing system according to claim 21, wherein: themask substrate is used for forming an EUV exposure mask.